This circuit is from a 1980s Motorola documentation. The circuit makes use of old components that can in some cases be exchanged for modern equivalents.
This basic Schmitt trigger was found in an American publication from 1968. The circuit uses...
This circuit is from an American 1964 documentation. Transistors of the time are used, but modern...
This simple circuit uses small speakers for both listening and speaking (microphone). The feeding is...